Bierl



Feb. 7, 1956 Filed June 6, 1952 BIERL 2,733,628

KEY CONTROL OF ATTACK AND DECAY IN ELECTRONIC MUSICAL INSTRUMENT 9 Sheets-Sheet 1 INki/VTQJE W/CH/MD B1294 Feb. 7, 1956 R. BIERL 2,733,628

KEY CONTROL OF ATTACK AND DECAY IN ELECTRONIC MUSICAL INSTRUMENT Filed June 6, 1952 9 Sheets-Sheet 2 r0 sou/x5 0F NEG/1 7/ v5 POTENTIAL P/TC/Y CO/VT/FOL Z3 37 7'0 CONTROL c/ecu/r g5 24 AND SOURCE OF T0 P/TCH colvrkaL 7o con/W04 C/RCU/f ,q/va T0 SOURCE OF SOURCE OF POS/T/VE NEGA77l/E POTENTIAL l 45 Pom/V7741- Feb. 7, 1956 R. BIERL 2,733,628

KEY CONTROL OF ATTACK AND DECAY IN ELECTRONIC MUSICAL. INSTRUMENT Filed June 6, 1952 9 Sheets-Sheet 5 INVE r p 530mm 3/5/9 Feb. 7, 1956 R. BIERL 2,733,628

KEY CONTROL OF ATTACK AND DECAY IN ELECTRONIC MUSICAL INSTRUMENT Filed June 6, 1952 9 Sheets-Sheet 4 I mew rag, Maw; 3/5/9 Feb. 7, 1956 R. BIERL 2,733,628

KEY CONTROL OF ATTACK AND DECAY IN ELECTRONIC MUSICAL INSTRUMENT Filed June 6, 1952 9 Sheets-Sheet 5 fig 7 AND 70 SOURCE 0F POI/7W5 PWL-Wr/AL E-D- 0/? 70 500/705 0F A/fG/UYI/f POE/V7744 7'0 CONTROL C/ACU/f rmmg 5 POTENTIAL 0,? m & 95 H sou/m? 0F MFG/WW5 T0 P/fCH POTEN MIL (ONT/POL fig. 12

17v GE V7019.

Feb. 7, 1956 R. BIERL 2,733,623

KEY CONTROL 0F ATTACK AND DECAY IN ELECTRONIC MUSICAL INSTRUMENT Filed June 6, 1952 9 Sheets-Sheet 6 i f 6 To 64 AMPZ/F/ER B 68 ,ZNVF/Vfdk 7/5141?) 3 594 Feb. 7, 1956 R. BIERL 2,733,628

KEY CONTROL OF ATTACK AND DECAY IN ELECTRONIC MUSICAL INSTRUMENT Filed June 6, 1952 9 Sheets-Sheet 7 722 saunas 0F Pw/HVE OTENT/AL NEG/"7V5 POTENTIAL I N y 5N 7' 01?: E oy/mp 3/594 Feb. 7, 1956 R. BIERL 2,733,623

KEY CONTROL OF ATTACK AND DECAY IN ELECTRONIC MUSICAL INSTRUMENT Filed June 6, 1952 9 Sheets-Sheet 8 PITCH CON TROL CONTROL P/ TC H CON TROL [MR i I I72 i i 9- 14 12/ PITCH CONTPQL Off/Hi7 pus/4 PULL 25 AMPLIFIER Fig. 5

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Feb. 7, 1956 R. BIERL 2,733,623

KEY CONTROL OF ATTACK AND DECAY IN ELECTRONIC MUSICAL INSTRUMENT Filed June 6, 1952 9 Sheets-Sheet 9 ro 0304mm? AMPL/F/ER AND PITCH co/vmoz.

,445 CONT/F01. 157 I39 CIRCUIT 154 KEY OPEPATED sw/rclmve ARRANGEMENT P/ TCH CO/VTEOL AMPL/F/Ek I59 Hg. 17

JJv/aww? United States Patent KEY CONTROL OF ATTACK AND DECAY IN ELECTRONIC MUSICAL INSTRUMENT Richard Bier], Trossingen, Germany, assignor to Matthias Hohner, Aktiengesellschaft, Trossingen, Germany, a corporation under German law Application June 6, 1952, Serial No. 292,046

Claims priority, application Germany June 8, 1951 7 Claims. (Cl. 84-126) This invention relates to musical instruments, and in particular to electronically operated keyboard instruments.

it is an object of the present invention to provide means facilitating production of musical sounds by keyoperated instruments in which the keys are employed either to control directly the frequency output of electrical oscillator circuits or to actuate auxiliary mechanical means operable in turn to control electrical oscillations in appropriate circuits, as well as to control an amplifier for said oscillations.

it is another object of the present invention to provide means affording exercise of a high degree of control over the quality of the musical sounds produced by electronically operated, keyboard instruments, such control being effectuated in an improved manner and with considerably high efiiciency by means controlling, independently of one another, the attack and decay of the various musical notes.

it is still another object of the present invention to provide means contributing to greatly simplified, yet highly sensitive electronically operated musical instruments wherein the musical sounds may be produced by electronic means working alone or in conjunction with mechanical sound generating means.

A further object of the present invention is to provide means redounding to novel and efficacious keyboard instruments incorporating switch-controlled electronic sound generating systems, the articulation of the sounds produced by said instruments depending either on the force with which the keys thereof are operated or on the extent to which said keys are displaced from their rest position.

More particularly, it has been known that musical effects capable of being produced by means of mechanically operated musical instruments of known design, such as stringed or wind instruments, depend not only on the intensity of the sound, the presence or absence of even and/or odd harmonics and the naturally occurring transient phenomena, such as building-up and decay phenomena, but also on the nature of the beginning and the end of the sound (marginal zones) and on the pattern followed by the sound between said marginal zones, that is to say, on the musical articulation of the sound. It has also been known that the person playing an instrument having the above-mentioned characteristics can, Within certain limits which are characteristic of the instrument under consideration, control the quality of the musical articulation. in doing so, the player of the instrument controls in a decisive manner the character of the musical interpretation.

In order to enable this control of the character of the musical interpretation to be exercised also in the case of musical instruments having means for generating electrical oscillations and means for controllable amplification (electronic-type musical instruments), the present invention provides for the beginning and the end of the 2,733,628 Patented Feb. 7, 1956 musical articulation to occur within independently predetermined ranges of their respective time constants as a result of the manner in which the actuating members corresponding to the notes of difierent pitch are operated, the said actuating members being provided with additional switching means serving the purpose of initiating the operation of a gain control system. By designing the actuating members in the manner hereinbefore described and by thus providing means serving to influence the beginning and the end of the articulation it is possible, using an extremely simple playing technique, by merely changing the manner of operation of the said members, to thereby control the character of the musical effects at will and within wide limits and, for example, to match them with certain natural acoustical phenomena or, where desired, fully to take into account the inherent charac teristics of an electronic musical instrument.

According to special embodiments of the invention, the functioning of the above-mentioned additional switching means may be made dependent on the magnitude of the impulse (momentum) impressed upon the actuating member or the said functioning may be made dependent on the magnitude of the displacement of the said actuating member. In the case of the first-named embodiment of the invention (dynamic method), the necessary contact or contacts can be made by at least one of the free ends of a two-armed lever which is pivotally mounted, preferably at a location coinciding with its centre of gravity, on the actuating member which follows a path that at least approximates a straight line. In the case of the secondnamed embodiment of the invention (displacement method), there is provided between the operating positions of the switchserving to change the condenser charge-these changes corresponding to the beginning of the articulation and its stationary phase on the one hand and to the end of the articulation on the otheran additional operating position, the switch, when in this position, serving to disconnect the amplifying system in accordance with a time constant of its own which can be selected at will, whilst the operating condition of the oscillator is maintained unchanged.

The above-mentioned requirements with regard to the articulation can only be fulfilled satisfactorily if the complex resistance of the control member of the amplifier stage-which control member may, for example, comprise a condenser as well as a charging and a discharging resistanceis dimensioned in such a manner that the said resistance, when represented with respect to the input side, exceeds the internal resistance of the input circuit which may, under certain circumstances, be complex in nature. According to the invention, another improve ment can be obtained by providing for a certain portion of the capacity of the control condenser to be disconnected at at least one pole from the amplifier system, while the condenser is being discharged. This serves to shorten the decay of the articulation to a particularly great extent.

Additional features of the invention will become apparent as the description proceeds, the description being taken in conjunction with the accompanying drawings which illustrate, by way of example, certain embodiments of the actuating member together with additional switching means as well as certain embodiments of the gain controlling circuits controlled by the said switching means. Figures 1, 2 and 3 on the one hand and Figures 4, 5, 6 and 7 on the other respectively show ditferent views of such actuating members together with their structural details. Figures 8, 9, 10, 11 and 12 represent the arrangement and the manner of operation of switching means permitting the employment of the hereinbefore described socalled displacement method. Figures 13, 14, 15, 16 and 17 illustrate circuit diagrams of the controllable amplifier stages.

masses Referring now to Figure 1, contact sprin pairs 1 to a, of which only the lower ones of each pair are visible in Fig. 1, are attached to a set of plates or strips which, in tion, is secured to the mounting bar 10. As will be seen from Figure 2, said set of plates or strips comprises the strip-like components 11, 1'2 and 13. The mounting bar also carries the soldering lugs, for example 14 and 15. Secured between the strip-like components 11 and 12 on the one hand and 12 and 13 on the other are the contact springs, for example 17 and 18, of the aforesaid pairs 1 to 9, which are arranged for co-action with the respective actuating members, that is to say in a stricter sense, with the corresponding carrier members, shown for example at 16. Depending on the arrangement of the pitch control circuit of the oscillator, the plate or strip 13 may consist either of a suitable metal or a suitable insulating material. The bar 10 and the strips 11 and 12, however, are always made of a suitable insulating material.

The mounting plate 10, together with the set of strips 11, 12 and 13, is attached to the keyboard frame 19. In addition, this frame carries the slotted mounting blocks 20 and 21 (see also Figure 2 and Figure 3). Contact spring groups such as shown at 22, are guided in grooves provided in said mounting blocks. The electrical connection between the individual groups of contact springs is established by means of wires arranged in longitudinal slots 23, 24 and 25 extending parallel to the mounting block. Pairs of contact springs, such as shown at 28, 29, are arranged in transverse slots, such as shown at 26, 27, which are provided in the block 20. One contact spring of any given pair of springs is connected in series with one contact spring of the next adjacent pair. The rod 30, which consists of a suitable insulating material, serves as an abutment for the pairs of contact springs.

} From Fig. 1 the actuating members, namely the keys 31 and 32 are clearly apparent. The actuating member 31 forms a structural unit with the carrier member 16. In the free end of the carrier member 16 there is pivotally mounted at 33 the two-armed lever 34 the free ends of which are fitted with inertia bodies or masses 35 and 36, respectively. In order to provide for a compact design, the inertia masses are concentrated to the greatest possible extent in the bodies 35 and 36, the result being that twice the length of the radius of gyration of the twoarmed lever 34 approximately equals the length of said lever. That free end of the lever 34 which carries the inertia body 36 is further fitted with a small contact plate 37 which, whenin its position oi rest, presses against the pair of springs 28, '29. The bearing or pivot 33 approximately coincides with the centre of gravity of the twoarmed lever 34. The movement of the actuating member 31, e., the white key, member 32 being a black key, together with the carrying member 16, is eflected against the resistance of an energy storing device such as a spring (not shown in the drawing) which is under a high preload, the said movement being limited by the bar 33 which serves as a stop member. In order to damp the impact of the carrying member on the bar33, the latter is lined with a suitable resilient material, for example felt or rubber.

The carrying member 16 is fitted at least with an abut ment shoulder 39 designed to engage that free end of the two-armed lever 34 which carries the inertia body 36. In addition the carrying member 16 has a projection 40 serving to establish contact between the contact springs 17 and 1.8 upon depression of key 21.

The movement of the free end'of the two-armed lever 34 which carries the inertia body 35 is blocked by the hinged member'41, the position of which determines the maximum deflection of the two armed lever. The hinged member 41 may be swung about an axis 42 disposed parallel to stop ba'r 3'8 which limits the stroke of the actuating member 31 together with its carrier 16. Hinged member 41, which may be fixed in position as indicated 4 below, is biased in one of its directions of swinging movement by a spring or similar energy storing device (not shown). An eccentricor Wedge-operated mechanism (not shown in the drawing) is provided for the purpose of controlling the deflecting position of the hinged member 41.

When the actuating member 31 together with its carrying member 16 and the two-armed lever 34 supported by the carrying member is displaced from its original position by a strong impulse, the two-armed lever will be displaced parallel to itself. During this operation the contact between the contact springs 23, 23 and the contact plate 37 is opened and the pair of springs 23, 29 are permitted to engage the rod 3% which is held in position by the supporting member 3t (see also Figure 1). As will be described later, this has the efiect of disconnecting control condenser system 14-6 to 143 (Fig. 16) from a source of negative potential 153a, this condenser system being later used to control the gain of an amplifier stage 138 to which electrical oscillations are fed. Upon continued movement of lever 34 contact together with plate 37, the latter will engage the group of contact springs 22. This, in turn, results in the said condenser being brought to a more positive potential, in consequence whereof the amplification is increased. Moreover, the movement of the carrying member 16 has caused its projection 4-0 to establish an electrical contact between the contact springs 17 and 18. In this manner the pitch control circuit has been rendered operative, this preferably being done before contact is established at the group of contact springs 22.

The elastic forces exerted by the group of springs 22 impart a rotary acceleration to the two-armed lever 34, the result being that after some time has elapsed the contact between the plate 37 and at least one spring contact of the group 22 is opened. In this position of operation the potential of the condensers 146 to 142% which furnishes the control voltage is changed to a negative value which brings about reduction in the amplification. As soon as the actuating member 31 is released, the energy storing device serving to return this member to its original position becoming operative, the fulcrum 33 of the twoarmed lever 34 is returned through the agency of the carrying member 16, the result being that the contact plate 37 again engages the pair of contact springs 28, 29. This causes the changeover of the condensers 146 to 148 to a negative potential. In addition, the pitch control circuit is interrupted by the contacts 17 and 18 being separated.

When only a weak impulse is imparted to the actuating member 31, the hereinbefore described displacement of the two-armed lever, without any rotation being imparted to it, will no longer be observed. Admittedly the fulcrum 33 is positively displaced through the agency of the carrying member 16, but at the same time the action of the group of springs 22 Willrot'ate the lever 34 in an anti-clockwise direction (see Figure 2). The spring contacts 17 and 18 as well as the pairs of springs 28, 29 are operated in a manner explained hereinabove. The mode of operation just described prevents the group of contacts 22 from being closed, the result being that the amplification is not increased. The return travel of the actuating member 31 under the influence of the energy storing device is'effected in the manner already described.

It the impulse values which areimparted by the actuating member 31 range between the two operating conditions hereinabove mentioned, then the corresponding charging periods will vary between the first (maximum) and the second value (zero). Owing to the building-up and decay phenomena produced in this manner, the naturalncss of the sound produced is improved and it is further possible for theplayer of the instrument to control the intensity of thesound at will. This possibility becomes important forthe aforesaid manner'of operation wherebywith one andtlie'same operating means 'orkeys besides the electric (electronic) sound eifect, use is also made of mechanically created sound production.

Further advantageous musical efiects may be obtained by transition or changeover to continuous notes whereby the hinge member 41 by suitable adjustment means is operated to assume a position apparent from Fig. 2 where by the inertia body 35 on the free end of the doublearmed lever 34 is prevented from further rotational movement. As will be understood from the foregoing, the group of springs 22 in this case remains short-circuited as long as the actuating member 31 is kept depressed. During this period, this contact connection will then maintain a given positive potential on the condenser system, in consequence whereof a corresponding constant degree of amplification is maintained.

The embodiment illustrated in Figures 4, and 6 mainly differs from the hereinbefore described embodiment in that in the former the two-armed lever 44 is returned by the stationary stop member 45 which at the same time serves to guide the carrying member 46. The free end of the extension 47, which latter forms a unit with the said carrying member 46, is provided with the slots 48, 49 and 50 of different depth, these slots receiving the stationary contact elements 51, 52 and 53. When at rest, the said contact elements engage the stop bar 54. Level 44 carries inertia bodies 59 and 59a at its ends.

The spring contact means 28 and 29 and the contact plate 37 which form a contact point according to Fig. 2, as well as the pitch control switch means 17, 18 correspond to the switching device 55 as seen in Fig. 5. The pitch control is aifected by the contacts 56 and 57 while the disconnection of the condensers 146 to 148 from the negative potential at 153 is efiectuated by cooperation of the spring contact means 58 with the inertia body 59 of the two-armed lever 44. It is to be noted that the switching operation occurs in stages, e. g. due to the displacement of the two-armed lever 44 together with its rotational movement counter-clockwise whereby first the contacts 56 and 57 are connected with each other and thus establishing the pitch control circuit. Only thereafter the engagement between the pair of contacts 58 and the inertia body 59 is interrupted, which corresponds to the breaking of contacts 28 and 29, this action causing the condenser to be disconnected from its negative potential.

On further downward movement of the carrier member 46, the inertia mass 59a strikes the group of springs 51, 52, 53, and interconnects them, serving to connect the control condenser to an amplifier and to a source of positive potential and thus increase the gain of the amplifier. Prior to this, however, extension 47 has come into engagement with contact springs 51, 52, and 53, to hold two of them at the same level, by virtue of two of said slots, and to hold the third contact spring at a lower level by virtue of the third slot, so that mass 59a first connects the condenser system to the amplifier and subsequently to the source of positive potential, by suitable arrangement of the electrical connections. The resilience of the group imparts a counter-clockwise rotation to the lever 44, which is limited by a stationary stop 45 and causes the contact between them to be broken again in an order which is the reverse of that just described. The stop 45 also serves to restore the lever 44 to the horizontal position when the key 31 is released.

According to Fig. 7, the invention contemplates a different arrangement of a switch group similar to 55, but in which operation is effected by the downward movement, i. e., toward the switch group, of a nose 46a on carrier 46 itself, in contrast to switch group 55, which is operated by movement of the inertia mass 59 away from the group. In the arrangement of Fig. 7, on depression of the key 31, nose 46a on carrier 46 first closes contacts 60 and 61 to establish the oscillatory or pitch control circuit. Further movement causes an insulating pin 62 on contact 60 to push a pair of side-by-side contact springs 63 away from a shorting contact bridge 63a to disconnect the control condenser system from a source of negative potential, in the manner of contacts 28, 29 of Fig. 2 or 58 of Fig. 5. The control condenser systern is connected to a source of positive potential by an arrangement such as that shown in Fig. 5 for that purpose.

In these two arrangements described with reference to Figs. 1 to 7, the contact springs 1 to 9 (Fig. 1), 17 and 18 (Fig. 2), 56 and 57 (Fig. 5), and 60 and 61 (Fig. 7), control electrical circuits which determine the freouency or pitch of the note emitted (for example LC circuits in normal oscillators and RC or RL circuits in relaxation oscillators). The contact springs allow the connection in the oscillatory circuit of a frequency-determining component of appropriate value for the pitch corresponding to the particular key depressed.

The embodiments of the invention described in the foregoing are based on the dynamic method mentioned earlier in this specification. This method proves to be of par- "cular advantage in cases where a musical instrument having an electronic oscillator is combined with an instrument in which musical sounds are produced by mechanical, that is to say, by conventional means, and in which a single common keyboard is used. in such a case the manner in which the actuating members (keys) are operated eonstitutes the factor which decides the greater or lesser extent to which electronically produced musical effects are added to the production of mechanical sound effects. If, however, the last-mentioned combination, in one and the same instrument, of an electronic method of producing sound with a mechanical method of producing sound is dispensed with, one being satisfied with producing musical effects solely by electronic means, it is possible to produce the desired musical effects by means of the so-called deflection method hereinabove mentioned. It is possible to embody this displacement method of control either in electrical or in mechanical locking means which in either case are controlled by the actuating members already mentioned.

in order to obtain an electrical locking action of this sort, one can make use of a cascade switching arrangement as is more clearly apparent from Fig. 8. The charging condenser 64 which corresponds to the condenser of Fig. 16 and designated by numerals 146 to 148 will be switched over between the negative potential 65 (at 153 in Fig. 16) and the positive potential 66 (at to 152 in Fig. 16). in this predetermined position condenser 64 which is grounded at 67 comes to lie above switch 68 of the cascade switching arrangement 69 due to the connection of the Working contact 70 with the positive potential 66 by means of the conductor 71. The switch 72 which is also actuated in the same operation remains, however, ineffective. if the movable contact pieces (for instance, 68) of all the individual switches are in their positions of rest as it is exemplified in the drawing with respect to switch 73 and if the condenser 64 is consequently connected to the negative potential 65, then a respective control of the amplification in a diminishing manner is effectuated, for instance by means of a locking device for the amplification.

With a cascade switch arrangement according to Figure 8 it is impossible to control the transient phenomenon, that is to say, to produce another articulating action (se quence of tones), by operating an additional contact arm as long as any of the contact arms of the cascade arrangement rests on its working contact (for example, the contact arm 63 resting on its working contact 70), this being due to the hereinbefore mentioned fact that in such a case the operative position of any additional switch (for example, at 72) remains unefiective. If it is intended also in the case of such tone sequences to exercise the abovementioned control upon the next following key being operated, it is necessary to make use of an arrangement such as illustrated, for example, in Figure 9. Referring 7 to the operating condition illustrated in Figure 9, it will be seen from the respective positions of the individual contact arms of a multiple (dual) cascade switch arrange mentthese positions being indicated by heavy lines that thc'condenser 74, which represents the control condenser, is connected with the positive potential 75. in this case, the key corresponding to the switch 76 has been depressed. As soon as that key which corresponds to the switch 77 is operated, while the key corresponding to the switch 76 is kept in its operative position, that is to say, as soon as the contact arms of the switch 77 are moved into the position indicated by dotted lines, the condenser 74 is connected with the negative potential 78. Due to the charge of the condenser 74 being changed as a result of this operation, a new controlling action upon the transient phenomenon is prepared, this controlling action beginning as soon as the key corresponding to the switch 76 is returned to its rest position. Thus, there results the possibility, merely by changing the manner of operating two actuating members, to change over at will between legato, portato and staccato. it follows that it is possible by using this dual cascade switch arrangement according to Figure 9 to interrupt the amplifying action momentarily, this interruption lasting as long as at least two actuating members are kept depressed and the corresponding contact arms remain in their respective operating positions. This mode of operation shown in Fig. 9 may be applied also to the dynamic method, referred to and described earlier in the specification.

in Figure 11 the key itself is indicated by the numeral St). The key 30 carries the extension 81 in the free end of which the slots 82 are provided. These slots serve to guide the contact elements 83, 84 and 35 which, when at rest, engage the stop member 86. The contact plate 87 which is provided with a groove 83, in one operating position causes the contact elements 83 to 5 to make contact, while in another operating position it causes only the Contact elements 83 and 85 to make contact. When the said contact plate is shifted from the one operating position to the other, the amplifier circuit is disconnected with a time constant of its own which can be selected at will, while the operating condition of the input circuit remains unchanged. Thus there results the naturally-decaying short-stroke tone. The pairs of springs mentioned in conjunction with. Figure 2 are indicated in Figures and ii by the numeral 89. The pair of contacts 7, correspond to the pairs of contacts 17 and 18 of Pi g. 2 and serve to establish an oscillatory circuit of appropriate frequency on depression of the key 80. An insulating pin 7% on one of the contacts 79 pushes contact spring 89 away from stop 86 to break the connection of the control condenser to a source of negative potential.

Fig. 12 illustrates an embodiment of an actuating member together with its switching arrangement. The actuating member as (for instance a white colored key) with its extension 91 carries a nose @2. The switching arrangement i designated in Fig. 16) is constituted by contact pins 93 which are arranged successively in slots of the nose 92 (corresponding to 43 to 53 in Fig. 5) and through contact. plate 94 which is afiixed to the extension )1. On the lower spring contact of the pair of contacts 95 which again serve for the pitch control an insulation pin 96 is atlixed which extends through the upper spring contact and acts on the extension 91 of the actuating member 9i? in corresponding position of the latter. The actuation of key 9% is brought about in several ph. a". First of all the extension )i comes in contact with the resilient base 97 of the hearing or abutment 93. Above the insulating pin 9'6 the pair of spring contacts 95 are then in open position and the oscillation action of a single generator is established which shows the conventional build-up for LC generators. The capacitance is composed of parallel condensers which are connected with each other through switch 95 according to a grouping corresponding to the respective tone pitch. Upon further depression of the actuating member '90, closing of the contact between s'uccessive contact pins is effectil'at'ed whereby the Contact plate 94 upon compression of the resilient liner 97 establishes the corresponding electrical connection at 22. in Fig. 16. Upon return of the actuating member to its position of rest which is determined by the abutment of the nose 3 against a resilient abutment 99 consists of several layers, contact connection between the aforesaid spring contacts is re-established and the oscillating action of the generator is interrupted whereas the known short-circuitiug of the total capacitance occurs. The abutment 99 may consist of alternating rigid and resilient layers in order to afford simultaneously a substantially noiseless and uniform abutment.

The arrangement hereinabove described in connection with Figs. l to ]2 refer in particular to actuating means for the release of electrical compensating operations as they are applied in musical instruments which are provided with an electric oscillator circuit. According to the operation of the actuating members and commensurate with their operation the respective responses are brought about which during their action on the respective control amplification stages result in a desirable articulation with electrical oscillations at the output of the controllable amplifier stage. According to Fig. 13 the input circuit 100 of such a controllable amplifier stage 101 which contains the complex inner resistance W2 is connected through a transformer .ltllf; with the amplifier circuit 104. This latter circuit is connected to the output circuit 105 and contains the ballast resistance 186. The transformer 1133 may operate as such or a storage element 163 symbolically indicating that a switch is employed which according to its purpose is composed of a transformer and a resistor 107 having a non-linear characteristic (electronic tube).

it has already been mentioned that the requirements here under consideration as regards the articulation may be fulfilled in a desirable manner. Consequently, the articulation is to be independent from the tone pitch and from the frequency of the controllable amplifier stage from the time element for the articulation (secondary requirements for the articulation).

To this end, the decoupling effect is so harmonious in accordance with the present invention that the complex resistance of the control member 108 transformed to the input side ltltl will be larger than the complex inner resistance 1&2 of the input circuit. The control member 108 including the condenser and the charging and discharging resistance therefor is loosely coupled with the resistance M7. The de-coupling resistance is designated by numeral m9. in accordance with an improved embodiment the aforesaid de-coupling system may contain a push-pull system as it is apparent from Fig. 14 in which the input circuit. 116 contains the complex internal resistance 111.

The switching actions caused to occur upon the actuating member :76 being depressed correspond to an operation of arrangements illustrated in Figures 8 and 9.

The latter is connected with the output circuit 112 by way of the push-pull system 113. The push-pull transformer iii 6, the place of which may also be taken by the coil of an electromechanical pick-up this coil being split in two halves-is connected with the amplifier circuit 115 on the one hand and with the amplifier circuit 116 on the other. (To. nected in the amplifier circuit 115 is the resistance ill? which has a non-linear characteristic. This resistsure is controlled by the control network 118 which, by way of example, may consist of a condenser and a charging and a discharging resistance. in the latter case, the coupling resistance is indicated by the numeral 119. The amplitier circuit lid comprises the resistance 224i which has a non-linear characteristic and with which there is loosely coupled the control network 121 which is arranged in the same way as the control network 11.8, or with which there is loosely coupled the; control network 113 itself. The decoupling resistance is indicated by the numeral 122.

Referring to the amplifier circuits 115 and 116 of the push-pull system 113, it should be observed that as far as the real or the symbolic meaning of the push-pull amplifier and the resistances 117 and 120 are concerned, the same statements apply that have earlier been made with regard to the transformer 103 and the resistance 107 in Figure 13. As regards the magnitude of the decoupling effect of the control networks 118 and 121, respectively, the same condition applies that constitutes one of the main features of the invention and which has been emphasized in conjunction with the description of Figure 13.

The output voltage is supplied by way of the push-pull transformer 123 and is introduced into the output circuit 112. The latter circuit comprises the ballast resistance 124.

According to Fig. 15 a particularly advantageous embodiment of the invention is illustrated. The input circuit 125 which contains the complex internal resistance 126 is connected with the push-pull system 128 by way of transformer 127, the output side of said system being indicated at 129. 130 indicates a resistance of the output circuit having different values of resistance to direct current and alternating current respectively (primary winding of an output transformer). The push-pull system 128 consists of two circuits 131, 132 operating on the pushpull principle. The resistances 133, 134 have non-linear characteristics whereas the two amplifier circuits 131 and 132 are connected to this resistance, respectively. The control network 135 is provided in the common conductor 136 of the two amplifier circuits 131 and 132. This network also includes a condenser and a charging and discharging resistance. On account of the arrangement of the control network 135 in the common conductor 136 the complex resistance in View of its transformation on the input side will be considerably increased in comparison with the complex internal resistance of the input circuit.

In the case of the embodiment illustrated in Figure 16, the input circuit 137 is also connected with the output circuit 139 by way of a push-pull system 138. The resistances which have non-linear characteristics are respectively constituted in one branch of the amplifier circuit by the multiple-grid vacuum tube 143 and in the other branch of the amplifier circuit by the multiple-grid vacuum tube 144.

Again in this case, the control network 145 is constituted by a condenser, a charging resistance and a discharging resistance. As an alternative to this embodiment, there may also be provided a chain circuit comprising pluralities of condensers and resistances, this circuit being so arranged that the charging resistances are connected in the longitudinal branches, while the condensers are connected in the transverse branches. Whereas in the case of the embodiments described thus far in this specification only a single condenser and a single charging and discharging resistance was mentioned, the condenser in the case of the control network 145 is composed of the elements 146 to 149. The elements 146 to 148 may by choice be connected in parallel or in the place of one another. in the case of the control net- Work 145 the charging resistance, too, comprises the different-sized elements 150 to 152 which may also be connected in parallel or in the place of one another.

Condenser 149 is permanently connected between the screen grids of vacuum tubes 143 and 144 and ground independently of the key controlled switches. The switching arrangement, generally designated as 154, is electrically interposed between a source of negative potential 153a and a source of positive potential 152a.

In switching arrangement 154, three switches 154b, 154a, and 154d, corresponding to three keys of the instrument, are shown in rest position, while a fourth, generally designated as 154a, is shown making the connections which result when a key is depressed.

The lower contacts 28 and 29 are those referred to above with reference to Fig. 2. As previously set forth, they correspond to, and have the same function as contact springs 58 of Fig. 5, contact springs 63 of Fig. 7, and contact springs 89 of Fig. 11. The upper contacts 22 (shown vertically above contacts 28 and 29 in Fig. 16) correspond to, and have the same function as contact springs 5152-53 of Figs. 5 and 7 and contact springs 83-84--85 of Fig. 11. With respect to Fig. 12, contact springs 93, in eifect, combine the functions of both contacts 22 and 28-29. Contact plate 37 normally interconnects contacts 28 and 29 or their counterparts, but the connection is broken when a key is depressed (corresponding to upward movement of switch 154a as seen in Fig. 16). Depression of the key later causes plate 37 to interconnect the group of contact springs 22 or their counterparts, interconnecting two of them first, and then connecting the third to these two a short time thereafter.

Depression of a key, thus, first breaks the circuit which had previously existed from one side of the control condenser group 146 to 148 through leads 169 and 176 switches 154a to 154d at rest, and discharging resistor 153 to the source of negative potential 1530. Depression of the key thereafter establishes, through lead 169, two of the spring contacts 22, and lead 171, a circuit from that same side of the control condenser group to the screen grids of pentode tubes 143 and 144. The other side of the control condenser group is connected permanently through a lead 142 to the common and grounded cathode terminal of the two tubes. On further movement of contact plate 37, the third one of spring contacts 22 then connects that side of the condenser group to which thescreen grids are connected to said source of positive potential 152a through charging resistors 150, 151, and 152 connected in parallel. One or more of these resistors may be switched out of the circuit, in order to increase the time constant of the control condenser charging circuit, if so desired.

As a charge builds up on the control condenser group or system 146 to 148, the potential on the screen grids of pentodes 143 and 144 rises and the audible output from loudspeaker 15?: increases. In this way the rate of increase of volume of sound, that is to say the attack of the note is determined by the capacity of the control condenser system and the value of the charging resistances 150, 151, and 152 to which the condenser system may be connected. The amount by which the volume increases for given values of these circuit components, and hence the maximum amplitude of the note attained between attack and decay, depends on the value of the positive potential 152a and on the duration of time for which the connection is maintained, and this, in turn, depends on how long the contact plate 37 interconnects all of the spring contacts 22. It has already been described how this time depends on the force with which the key is struck.

When the contact at 22 is broken, either on rotation of the arm 34 (Fig. 2) or 44 (Fig. 5), or as the key rises (Figs. 7, 11, and 12), the control condenser group is disconnected from the source of positive potential and reconnected to the source of negative potential, whereupon it discharges at a rate determined by the value of discharging resistor 153 and the negative potential. This controls the decay of the note sounded as it reduces the gain of the amplifier stage 138. It will be seen that in this way the attack and the decay of the note and the intervening period therebetween are controlled by two resistance-capacitance networks of independent and adjustable time constants.

When the player brings about an additional operating position between the above-mentioned operating positions of a given group of switches (one of the latter positions controlling the building-up and the stationary phase, the other position controlling the decay phase), the said additional operating position serving to disconnect only the 1 1 amplifying circuit with a time constant of its own which can be selected at'will as has already been mentioned, while the original operating condition of the input'circuit is maintained unchanged,he can, by using a short stroke, produce a natural decay of the tone pattern. When such a group of switches is fitted with an actuating member which effects the changes in the charge of the condenser as a function of the impulse (momentum) imparted to the actuating member, it is possible to have the length of the period during which the control condenser is connected with the charging potential correspond to the magnitude of the said impulse. By using the hereinbefore described dual cascade switch arrangement (see Ingure 9), it is also possible to'close the contacts for a short period in order to give the condenser a more positive charge, this being done by momentarily depressing simuh tancously at least two of the actuating members.

The condenser arrangement 146 to Mil is discharged by way of the discharging resistance E53, the switch arrange-- ment also being used in this case. The said ccndenser arrangement can be discharged by disconnecting part of its capacity at at least one pole from the amplifier elements 143 and 144, respectively, this being done during the discharging period.

The anode voltage of the push-pull system is introduced between the common cathode terminal 155 and the centre tap 15 of the primary winding of the output transformer 157. The secondary winding of the output transformer 1% is for example loaded by the speaker 158.

In the event the controllable amplifier stage 138 is merely an intermediate amplifying stage, the control volttage can be introduced into the anodes, that is to say, the control network would in this case be connected between the centre tap 156 and the cathode terminal 155'.

Fig. 17 illustrates an embodiment of the push-pull system 159 in place of electronic valves the resistances are used having non-linear characteristics designated by numerals 16d and 161 and which are in series with direct voltage sources withthc amplifier circuits 7.62 and 163. In this case, the resistances are constituted by dry-rectifier elements. Instead, however, there may be provided iron hydrogen resistances, crystal diodes, choking coils having iron cores which are bias-magnetized by direct current, or similar circuit elements. In the conductor 164 which the circuits 162 and 163 have in common, there is connected the ballast resistance 165 and, in addition, the control network 166. The output terminals of the system are indicated at 167. The switch arrangement 168 of the control member operates on the same principles as the switch arrangement 154 which has been described in conjunction with Figure 16.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent, is:

l. in an electronically'and mechanically operated m'usical instrument having oscillator means including circuit means therefor, condenser means, amplifier means and pitch control means operatively connected to said circuit means; a keyboard frame, key means supported by said frame and for movement by impulsefrom an initial position to respective operative'positions,first contact'spring means for operating said pitch control means, carrier means operatively connected with said key means "and movable with the latter, said carrier means being provided with a projection for actuating said first contact spring means, respective block means provided with sets of guide slots and mounted in superposed position to each other on said keyboard frame, a two-arm lever pivotally disposed on said carrier means and provided at one lever end with a contact plate, second contact spring means extending through said guide slots of one-of said block means and into the path of said contact plate, third contact spring means extending in 'guideslots of another of said block means and in transverse direction to said second contact spring means, said second contact spring means being adapted upon C0-E1Cti0n with said contact plate to impart greases to said lever a pivotal rotary movement in the direction toward said'fifstcontact spring means and away from said third contact spring means, abutment means for said third contact "spring means when the latter are disengaged from said contact plate, said second contact spring means being adapted'to act upon said condenser means for increasing amplification through said amplifier means, and biased means for returning said key means with said carrier means to said initial position.

2. In an electronically and mechanically operated musical instrument having means for generating electrical oscillations andincluding circuit means therefor, condenser means, amplifier'means and pitch control means operatively connected to'said circuit means; a keyboard frame, key means supported by said frame and for movement by impulse from an initial position to respective operative positions, first contact spring means for operating said pitch control means, carrier means operatively connected with said key means and movable with the latter, said carrier means being provided with a projection for actuating sai'd first contact spring means, respective block means on said keyboard and provided with sets of guide slots, a twoarmedlever pivotally disposed on said carrier means and provided at oneend with a contact plate, second contact spring'means extending through said guide slots of one of said block means and into the path of said contact plate, third contact spring means extending in guide slots of another of said block means and'in' the path of said contact plate to thereby bring about charge of said condenser means by anegative potential for decreasing the amplification, said second contact spring means being operatively connected to said condenser means to place same to a positive potential for increase of the amplification and being adapted upon co-action with said contact plate to impart to'said lever a pivotal rotary movement in the direction toward said first contact spring means and away from said third contact spring means, whereby operation of saidfi'rst contact spring means for the pitch control means is etfectuated prior to the effective operation of said second contact switch means for increasing amplification, abutmentmeans for said third contact spring means when the latter'are disengaged from said contact plate, and biased meansfor' returning said key means with said carrier means to said initialposi'tion.

3. in an electronically and mechanically operated musical instrument having oscillator means including circuit means therefor, condenser means, amplifier means and pitch control means operatively connected to said circuit means, a keyboard frame, key means supported by said frame and for movement by impulse from an initial position to respective operative positions, first contact spring means for operating said pitch control means for said 0scillator means, carrier means connected to said key means and movable with the latter, said carrier means being provided with a projection for actuating said first contact spring means, a two-armed lever pivotally disposed on said carrier means and provided at one lever end with a contact plate, second contact spring means extending into the path of said contact plate for actuation by the latter when one of said key means is in a predetermined operative position, third contact spring means extending into the path of said contact plate upon movement of said key'means into a further predetermined operative position, abutment means for-said third contact spring means when the latter are disengaged from said contactplate, said second spring contact means being adapted to act upon said condenser means'forregulating amplification through said amplifier means, and biased means for returning said key means with said carrier means to said initial position.

4. In an electronically and mechanicaliy operated musical instrument haying oscillator means including circuit means therefor, condenser means, amplifier means and pitch control'means operativcly connected to said circuit meansg a keyboard frame, key means supported by Said frame and for movement by impulse from an initial position to respective operative positions, first contact spring means for operating said pitch control means, carrier means operatively connected with said key means and movable with the latter, said carrier means being adapted to actuate said first contact spring means, a two-armed lever supported by said carrier means, second contact spring means for actuation by said key means and for establishing connection of said condenser means with a positive potential for increasing amplification, third contact spring means operable for placing said condenser means to a negative potential for decreasing said amplification, abutment means for said third contact spring means when the latter become disengaged during opera tion of said key means, said second contact spring means being adapted to act upon said condenser means for increasing amplification through said amplifier means, biased means for returning said key means with said carrier means to said initial position, and stop means for limiting operative positions of said key means.

5. In an instrument according to claim 4, including cascade switching arrangement in said circuit means for switching said condenser means between negative and positive potentials.

6. In an electronically and mechanically operated musical instrument have oscillator means including circuit means therefor, amplifier means, and pitch control means operatively connected to said circuit means; a keyboard frame, a plurality of keys supported by said frame for movement from an initial position to respective operative positions, first contact spring means for operating said pitch control means, carrier means operatively connected with each of said keys and movable with the latter, each of said carrier means being provided with a projection for actuating said first contact spring means, a two-arm lever pivotally disposed on each of said carrier means, a plurality of contact plates fixed to one end of each of said levers, respectively, second contact spring means extending into the paths of movement of said contact plates, third contact spring means normally in contact with said contact plates and extending into the paths of movement of said contact plates on the side of the latter remote from said second contact spring means, said second contact spring means being adapted, upon engagement with a respective one of said contact plates subsequent to movement of a respective key from said initial to said operative position, to impart to said one end of a respective lever a pivotal movement in the direction toward said first contact spring means and away from said second contact spring means,

abutment means for said third contact spring means when the latter are disengaged from said contact plates, said second contact spring means being adapted, upon engagement with a respective contact plate, to act upon said amplifier means for increasing the gain thereof, and biased means for returning said keys with said carrier means to said initial position.

7. In an electronically and mechanically operated musical instrument having means for generating electrical oscillations and including circuit means therefor, amplifier means, and pitch control means operatively connected to said circuit means; actuating means disposed for movement from an initial position to respective operative positions, first contact spring means for operating said pitch control means, carrier means operatively connected with said actuating means and movable with the latter, said carrier means being provided with a projection for actuating said first contact spring means, a two-armed lever pivotally disposed on said carrier means and provided at one end with a contact plate, second contact spring means extending into the path of movement of said contact plate, third contact spring means extending into the path of movement of said contact plate and operable, when in contact with the latter, to bring about a reduction in gain of said amplifier means, said second contact spring means being operatively connected to said amplifier means to apply a positive potential thereto, upon being engaged by said contact plate, to increase the gain of said amplifier means, said second spring means being adapted upon coaction with said contact plate to impart to one end of said lever a pivotal rotary movement in the direction toward said first contact spring means and away from said second contact spring means, whereby operation of said first contact spring means for said pitch control means is efiectuated prior to the effective operation of said second contact spring means for increasing the gain of said amplifier means, abutment means for said third contact spring means when the latter are disengaged from said contact plate, and biased means for returning said actuating means with said carrier means to said initial position.

References Cited in the file of this patent UNITED STATES PATENTS 2,301,871 Hanert Nov. 10, 1942 2,492,320 Riggen Dec. 27, 1949 2,563,477 Martin Aug. 7, 1951 2,580,217 Colombani Dec. 25, 1951 

